Magento – How to get the quote address object when user logged in

Instead of

    if (in_array($prodId, $_remove_ids)) $cartHelper->getCart()->removeItem($itemId)->save();

you should use something like this:

    if (in_array($prodId, $_remove_ids) && !$quote->getItemById($itemId)->isDeleted())
         $cartHelper->getCart()->removeItem($itemId);

The key here is that removing an item, sets the is_deleted flag and with this you can check if an item is already flagged for deletion. Also you don't need to save each one individually as long as the cart gets saved in the end.

So based on what you said I have now got a solution that I belive works 100% of the time and matched the items nicely.

When merging there are 3 things that can happen.

1. When the item is in both quotes it's qty is merged into the logged in customers item.
2. When the item is in the guest quote but not the logged in customer quote a new item is cloned into the logged in customer quote, and the item_id is added at some later time (that I couldn't pin point)
3. The item is in just the logged in customer quote nothing changes.

Because the for the first two possibilitys the item is in both the quotes I used the compare function to find when the items matched and populated the newIds and OriginalIds at that point.

We can then say if there was no match this item was not in the guest quote so just use the newId as there was no originalId.

protected $_source;

/**
 * @param Varien_Event_Observer $observer
 * @return Training_Merge_Model_Observer
 */
public function salesQuoteMergeAfter(Varien_Event_Observer $observer)
{
    $this->_source = $observer->getEvent()->getSource();
}

public function controllerFrontSendResponseAfter(Varien_Event_Observer $observer){
    if($this->_source) {
        $newOldArray = array();

        //Quote = Customer Quote
        //Source = Guest Quote
        $quote = Mage::getSingleton('checkout/session')->getQuote();
        $source = $this->_source;

        foreach ($source->getAllVisibleItems() as $item) {
            foreach ($quote->getAllItems() as $quoteItem) {
                if ($quoteItem->compare($item)) {

                    $newId = $quoteItem->getData('item_id');
                    $originalId = $item->getData('item_id');

                    $newOldArray[] = array(
                        "newId" => $newId,
                        "originalId" => $originalId
                    );

                    $quoteItem->setIsMatch(1);

                }
            }
        }

        //If there was no match so far then it's a new item and there was
        //no similar item in the old quote, we can therefore just take the
        //newId and set the original to null
        foreach ($quote->getAllItems() as $quoteItem) {
            if (!$quoteItem->getIsMatch()) {
                $newId = $quoteItem->getData('item_id');

                $newOldArray[] = array(
                    "newId" => $newId,
                    "originalId" => null
                );

            }
        }
    }


    return $this;
}